720p 24pn audio sync issues!

Bumpman

Bumpman

New member
Hi
I recently shot a music video involving a club filled with people dancing to a track played through a PA system off a cd player.
All of the audio burned to the cd were bounced (rendered) directly from the protools file in which they were created. As well i bounced down 48khz versions for sync and editing in final cut pro.
I shot the video on an HVX 200a using the format DVCPRO HD 720p 24pN onto the p2 cards. I dumped the files twice once during and once after the shoot through the firewire port of the camera to my apple macbook pro.
All of the files were then given to my editor who imported them onto his system and added them to a final cut session. The sessions were set up PROPERLY (?) using easy setup (DVCPRO HD 720 24p 48k) and all of the clips went onto the timeline without the "CHANGE SEQUENCE SETTINGS TO MATCH CLIPS?" dialog box popping up.
Ok. Now this is where it gets weird.
All of the clips audio will sync together on the timeline and be perfectly ready for editing, EXCEPT.... THEY WILL NOT SYNC TO THE ORIGINAL AUDIO TRACK FROM THE CD!!!!!
First i thought it was a 44.1 to 48 discrepancy and did another export of the file. But then again that would cause a pitch shift to happen, which does not occur. they are completely in pitch with one another. The audio of the clips will sync up for about a minute, then slowly flam, then by the end of the two beats are swinging hard against one another.
Soooooo..... I decided that if it was a problem with the camera speed of one kind or another, then if i recorded a live bounce of the song into the cameras XLR inputs it would sync with the clips on the timeline. but no it didnt.
this is a strange conundrum that i have no idea what is going on. Does anyone have any input on this problem?
 
Bumpman,

I am not sure of all the terminology you use so correct me if I have misunderstood. You filmed the event with the cam, and recorded audio at the same time. You then imported the content of the CD to your editor, and KaBoom. If this is the scenario, it is likely that the internal clock of both recording inputs, the cam and the CD don't match in time code. Different devices run at different speeds internally and over a period of time, the drift can be measured in seconds. Better devices usually means better clocks.

Grant
 
Guess Number 1: If this _CLUB_ had a DENON or the Like DJ CD player which allows one to beatmatch the records, the CD players pitch control could have been off from perfect 0.

Forget about the 720p24 Picture for a sec,

Take the raw camera audio you have which is in sync with the picture - (you should have 2 channels from the on-camera microphone and 2 empty channels), and take the CD (stereo pair) at 44.1 or 48 if you have it.

pull the 4 of them into Protools/Soundtrack Pro etc... and see where the drift occurs and how severe, and if the drift is uniform (as in song is 120BPM in Protools, but your live recording is 119.95BPM) etc... You can do the same in LOGIC, or any other multi-track editor that supports a metronome (Click Instrument). If doing it in PT, either your signal or the master song will have to be transformed as protools supports only one clockrate in a single session - so it will convert the audio region to whatever KHZ.

Also mute and un-mute your 44.1WAV to CD vs. your club audio and see if the pitch "key" is any different.
Also your musician should have exported a 48khz version of the track for you to use in video, FCP transposes 44.1Khz sources auto-magically...

I bet it's the lack of crystal lock on the club CD player though. two tracks cannot drift that far apart due to clock variances, where at say 90bpm your 1/2 measure out by minute 2. It has to be the pitch control on the playback device.
 
Last edited:
ggrantly said:
Bumpman,

I am not sure of all the terminology you use so correct me if I have misunderstood. You filmed the event with the cam, and recorded audio at the same time. You then imported the content of the CD to your editor, and KaBoom. If this is the scenario, it is likely that the internal clock of both recording inputs, the cam and the CD don't match in time code. Different devices run at different speeds internally and over a period of time, the drift can be measured in seconds. Better devices usually means better clocks.

Grant
Click to expand...

No he played 44.1Khz source CD, taped people lip-syncing along to it, then his footage is out of sync with the original track. Music video and all.
2 minute drift by syncopated 1/2 measure. Too much for clock drift.
 
My apologies for the delay. No internet all day. We used a CD boom box Aux out to the club PA. We've done 3 prior music videos with the same CD boom box and the same camera with no sync issues. We even tried an experiment by just recording the audio directly into the HVX via boom box & then directly from protools and still the same sync issue. Also were using the same sync clock & I/O interface with both protools & fcp set to the same settings so there shouldn't be any clock issues. As I was saying we do the same thing every time.... So strange but it's the first time that we recorded in 24pN????
 
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